Asklemmy

This isn't exactly what you were asking for, but thought I would share a funny story from a few years ago.

I had a problem player, fell asleep during games, made other players uncomfortable with unwanted advances, would say racist things in and sometimes out of character, etc. So I decided to have a bit of fun on what I knew was going to be his last session with our group. He had wanted a ring of invisibility or a powerful magical crossbow. I gave him both.

The ring was not the kind you wear on a finger though, and he had to spend a full minute to put it on as it required some.... prep, he was so embarrassed he never even tried to use it.

The Crossbow was hot pink, covered in glitter, and became soul bound as soon as he attuned to it which was as soon as he picked it up. It shot 4 Eldritch Blasts per attack action, and gave a free attack action every turn. It also compelled anyone within 100ft of the bow to refer to the wielder as Sparkle Bitch. Small price to pay, so he thought. Problem is, the Crossbow was a cursed item and after the wielder fired 20 shots, all the damage it dealt would be added up, multiplied by 10 and then dealt back to the wielder in an explosive cloud of pink glitter. I don't recall the total, but was easily 4 times the players max HP. He was pissed, and that's when I told him he was no longer welcome at my table.

More in line with your request though: A magical whistle, when you blow it, once per day you can summon an army of 1D6 chickens who will then follow you around until your next long rest. You can have the army attack dealing 1D4 damage multiplied by the number of chickens. The chickens are unkillable, and vanish in a cloud of feathers when you take your next long rest.